package usb;
import java.util.Scanner;

public class Test05 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int add=0;
        int num = 1;
        for(num=1;num<=100;num++){
            if (num%2==0) {
                add+=num;
            }
        }
        System.out.println(add);
    }
}
